Chapter 15 Precast Concrete Framing Systems

Precast Concrete

Defini/on

Structural

Architectural

What Can Be Precast?

Slab Elements Beams (& Girders) Columns Wall Panels Other

Precast Concrete

Advantages Produc/on @ Ground Level Controlled Environment (Plant vs. Jobsite) High Quality Formwork (OMen steel, reuse) High Quality Materials (5000 psi conc., HSS) Controlled Curing (High Early, steam cure, 24hr cycle) Erec/on Time & Condi/ons (quicker, no formwork required, no temperature restraints concrete already cured)

Precast Concrete

Disadvantages Elements large & heavy

Transporta/on Site Mobility Hois/ng / Erec/on

Less field modifica/on flexibility OMen Require a Topping Slab

Precast Slab Components

Solid Flat Slab more dead weight

* Hollow Core Slab

* Double Tee

Single Tee Stability during erection Depth vs DT

* most commonly used

Hollow Core Slab

Widths: 2, 4, 8 Thickness: typ. 6- 12

Manufacturing Process: Extruded - Most common, or Cast in layers (proprietary systems)

Uses - Intermediate Spans / Average Loading

Hollow Cores - some of non-working concrete eliminated

Reinforcing Units typically not prestressed

Edge Sloped

Typically Supported by: CMU, Concrete Steel

Joints

Erected with a Crane

Grouted Subsequent to Erection

Double Tee

Double Tees (Stacked in the Yard)

Uses: Heavier Loads Greater Spans

Depth 12 to 36

Casting Bed - Metal

Top Slab / Flange Reinforcing

Haunch Armor/ Reinforcing

Flange Anchorage

Coils of Cable (Tendons) for Prestressing

Hydraulic Stressing Machine

Stressed Cable

Broom - Rough Held down for Topping

Finishes

Broom - Exposed

Lifting Eyes

Precast Slab Manufacturing

Controlled Environment Cas/ng Beds Reinforcing & Embeds Pour, Finish, & Cure Validate Strength Removal from Bed (Transfer stress to Member) Plant Storage or Transport to the Jobsite

Camber

Precast Slab Erec/on

Transporta/on to the Job Site Erec/on Anchorage Bearing Pads Topping Slabs

Bearing Pads Typically between Double Tee & Support Member

Bearing Pad for I Beam

Beams & Girders

Reinforcing - Conventional, Prestress, or Combo

L-Shaped Beam & Inverted Tee Beam Prestressed

AASHTO I Beams used for a Bridge

Columns Columns

Typical Base Details

Support notches For exterior beam

Precast Wall

Arena / Coliseum Precast Seating

Arena/Coliseum

Arena/Coliseum Bearing Pad

Parking Deck

Precast columns., beams, double tees

Parking Deck

Precast spandrel beams

Parking Deck

Precast columns & spandrel beams

Parking Deck

Precast walls & double tees

Support haunch

Haunch Support for Double Tee Member

Parking Deck Erection

Parking Deck Erection

Precast Connec/ons Column Splicing

Reinforcing Dowels Grouted Bolted Connection

Precast Connec/ons Non-Moment Beam to Column

Precast Topping

Precast Highrise

San Francisco 495 Apartments 39 Stories 420 ft high Seismic Zone 4 Near the San Andreas Fault Tallest Building to Date (inc CIP) 6/14/99 ENR

Precast Used with other Structural Materials

Precast & Cast-in-Place Concrete

Precast & Masonry

Precast & Structural Steel

Fully Precast Structure

Range : Parking Decks Common to Highrise Buildings - Rare:

Minimal Industry Experience ($) Lateral Loading - Moment Connections

Parking Beck with Architectural Precast Exterior Panels

Architectural Precast Exterior Panels

Precast & Structural Steel

Staggered Truss System Structural Steel Frame with Hollow Core Floor Slabs

Precast & Cast-in-Place Concrete

PC Slabs & CIP Beams & Columns (common) PC Columns & Beams with CIP Slab (unusual)

Often less $ to form beam w/ slab forming

Precast & Masonry Masonry & Precast Hollow Core (common)

Architectural Precast

Architectural Precast Panels

Architectural Precast Panels

Architectural Precast Panels

Architectural Precast Panels

Architectural Precast Panels

Architectural Precast Panels

Architectural Precast Panels

Architectural Precast Panels

Architectural Precast Panels

Architectural Precast Panels

Precast Panel Anchorage

OMen Supports no Building Loading except: Its Own Weight Weight of Cladding (ex. stone) Single eleva/on of Glass & Glazing Transmits lateral forces to the structure

Anchorage to the Structure Embeds in PC Panel Embeds in Structure Welded or Bolted Lateral Support/Bracing (or 2nd connec/on)